This invention relates to a fuel injection system and more particularly to a fuel injection system that may be employed in a two cycle or ported engine.
The advantages of fuel injection over carburetion are well known. However, there are certain disadvantages with existing forms of fuel injection systems.
It is, therefore, a principal object to this invention to provide an improved fuel injection system for an engine.
The types of fuel injections systems previously employed fall into two general categories. These are those that employ direct cylinder injection, where fuel is injected directly into the combustion chamber, or manifold or scavenge port injection systems, where the fuel is injected not into the combustion chamber but somewhere in the induction system for the combustion chamber. Each type of system had certain disadvantages.
With direct cylinder injection systems, the injector itself is exposed to the high pressure and temperature in the combustion chamber when the charge is burning. In order to resist these high temperatures, it is necessary to use extremely expensive injectors. Also, the injector valve tends to become clogged with carbon and may render it either inoperative or have it fail to properly seal.
Although an arrangement has been proposed wherein the injector is disposed in the cylinder side wall so that it will be masked during at least a portion of the combustion cycle, these systems also require either a check valve to protect the injector during the combustion cycle when the injector is uncovered by the motion of the piston or, alternatively, the high pressure high cost type of systems must be employed. In addition, such placement can give rise to problems in inadequate vaporization of the fuel.
If, on the other hand, the fuel is injected into the induction system, then some of the advantages of fuel injection are not realized. That is, with direct cylinder injection it is possible to obtain some form of stratification so as to minimize the amount of fuel consumed and to control the emission of unburned hydrocarbons under low and mid range performance. However, when the injection is into the induction system, stratification is difficult to obtain.
There also has been proposed a type of injection which injects not only fuel but also air. This type of injector has been applied in either the direct or manifold systems of the type aforedescribed. However, it has the same disadvantages as previously noted and additionally is a more complicated type of injector since it requires a fuel injector, an air compressor, and a control for both the fuel injector and the opening and closing of the air injection valve. Also, this type of system may require a pressure regulator for regulating the pressure difference between the fuel pressure and the pressure of an air chamber in the injector into which fuel may be injected.
It is, therefore, a further object to this invention to provide an improved fuel injection system wherein the fuel injector achieves the advantages of direct cylinder injection without having to withstand the temperatures and pressure existent in the combustion chamber.
It is a further object to this invention to provide a fuel injection system wherein air or another gas can be employed to assist the vaporization but the complicated air/fuel injectors previously proposed are not necessary.
It is a further object to this invention to provide an improved air/fuel type of injection system wherein a simple fuel injector may be employed and the benefits of direct cylinder injection may also be achieved without the complication of conventional air/fuel injectors.
There is a further disadvantage with the type of fuel injectors previously proposed. For the most part, these injectors have an injection nozzle from which the fuel is discharged through an opening controlled by an injection valve. As a result of this construction, the fuel is sprayed in a generally conical fashion into the area where it is discharged. Because it is desirable to maintain a relatively small construction for the fuel injector and particularly its nozzle portion, the fuel spraying from the nozzle of the fuel injector is not dispersed over a wide area.
In addition, if the fuel injector sprays directly into the combustion chamber, it is normally mounted in the cylinder head of the engine and thus sprays downwardly toward the cylinder bore. However, when employed with two cycle engines, the porting of the engine generally is configured to achieve some scavenging through a predetermined flow pattern in the cylinder. The fuel sprayed from the injector nozzle normally is in a direction that opposes the scavenging action and hence the fuel may be dispersed due to these differences in flow direction and the desired degree of stratification can not obtained.
Although certain of these disadvantages can be avoided by mounting the injector in the cylinder rather than in the cylinder head, this means that the injector nozzle will be exposed to the movement of the piston as it reciprocates. In addition, it is still not possible to provide wide dispersion of the spray from the fuel injector and the fuel injector must be positioned in a spaced relationship relative to the ports of the engine. Hence, the scavenge flow through the cylinder can not be employed in conjunction with the injected fuel to further improve stratification.
It is, therefore, a further object to this invention to provide an improved fuel injection system for an engine which permits the fuel to be dispersed in any desired pattern and in a direction wherein stratification can be maintained in the injected fuel even when scavenging action is employed.